Much of the world's metal reserves are in low grade mineral deposits which contain relatively low percentages of metals. It is not generally economically feasible to recover metals from low grade minerals because the cost of processing such materials by conventional methods often exceeds the value of the recovered metal.
Another disadvantage of conventional methods is that they are generally limited to the recovery of one metal at the expense of sacrificing or discarding the other recoverable metals.
Conventional methods are also unsatisfactory because they may require the use of high temperature and pressurized autoclaves which introduce problems of maintaining pressure seals and proper agitation. Such autoclaves are also expensive to purchase and to maintain.